﻿using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace Mangox.Tookit
{
    public class DESHelper
    {
        private static string GetKey(string key)
        {
            string tmp;
            tmp = "--------";
            key = (key + tmp).Substring(0, 8);
            return key;
        }

        /// <summary>
        /// 使用DES加密，key输入密码的时候，必须使用英文字符，区分大小写，且字符数量是8个，不能多也不能少
        /// </summary>
        /// <param name="toEncrypt">需要加密的字符串</param>
        /// <param name="key">加密字符串的密钥</param>
        /// <returns>加密后的字符串</returns>
        public static string DESEncrypt(string toEncrypt, string key)
        {
            key = GetKey(key);
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            //把字符串放到byte数组中  
            //原来使用的UTF8编码，我改成Unicode编码了，不行  b
            byte[] inputByteArray = Encoding.Default.GetBytes(toEncrypt);
            //byte[] inputByteArray=Encoding.Unicode.GetBytes(toEncrypt);  

            //建立加密对象的密钥和偏移量  
            //原文使用ASCIIEncoding.ASCII方法的GetBytes方法  
            //使得输入密码必须输入英文文本  
            des.Key = ASCIIEncoding.ASCII.GetBytes(key);
            des.IV = ASCIIEncoding.ASCII.GetBytes(key);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
            //Write the byte array into the crypto stream  
            //(It will end up in the memory stream)  
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            //Get the data back from the memory stream,and into a string  
            StringBuilder ret = new StringBuilder();
            foreach (byte b in ms.ToArray())
            {
                //Format as hex  
                ret.AppendFormat("{0:X2}", b);
            }
            ret.ToString();
            return ret.ToString();
        }


        /// <summary>
        /// 使用DES解密，key输入密码的时候，必须使用英文字符，区分大小写，且字符数量是8个，不能多也不能少
        /// </summary>
        /// <param name="toDecrypt">需要加密的字符串</param>
        /// <param name="key">加密字符串的密钥</param>
        /// <returns>解密后的字符串</returns>
        public static string DESDecrypt(string toDecrypt, string key)
        {
            key = GetKey(key);
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            //Put the input string into the byte array  
            byte[] inputByteArray = new byte[toDecrypt.Length / 2];
            for (int x = 0; x < toDecrypt.Length / 2; x++)
            {
                int i = (Convert.ToInt32(toDecrypt.Substring(x * 2, 2), 16));
                inputByteArray[x] = (byte)i;
            }

            //建立加密对象的密钥和偏移量，此值重要，不能修改  
            des.Key = ASCIIEncoding.ASCII.GetBytes(key);
            des.IV = ASCIIEncoding.ASCII.GetBytes(key);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);
            //Flush the data through the crypto stream into the memory stream  
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();

            //Get the decrypted data back from the memory stream  
            //建立StringBuild对象，CreateDecrypt使用的是流对象，必须把解密后的文本变成流对象  
            StringBuilder ret = new StringBuilder();

            return Encoding.Default.GetString(ms.ToArray());
        }

    }
}
